1. Field of the Invention
The present invention generally relates to optical lenses, and more particularly to a complex optical lens.
2. Related Art
Currently, digital camera modules are included as a feature in a wide variety of portable electronic devices. Most portable electronic devices are becoming more miniaturized over time, and digital camera modules are correspondingly becoming smaller. Nevertheless, in spite of the small size of contemporary digital camera modules, consumers still demand excellent imaging. The image quality of a digital camera is mainly dependent upon the optical elements of the digital camera module.
Aspheric lenses are very important elements in a typical digital camera module. An aspheric lens can easily focus an image on an imaging point, because the aspheric lens can attain different refractive indexes via the selection of different materials and profiles for the aspheric lens. Therefore, an aspheric lens can avoid many of the image-forming problems of spherical lenses. In addition, with a single aspheric lens, the number of lens pieces in a camera is reduced. Thus the camera can have a reduced size. Two or more aspheric lenses are used in some cameras for high-quality image forming. Contemporary aspheric lenses are essentially made of glass or plastic.
Glass aspheric lenses are generally manufactured by way of glass molding. A glass molding machine operates at a high temperature and high pressure during the glass molding process. Therefore, core inserts are needed, and these must be accurately designed and manufactured. The core inserts should have excellent chemical stability in order not to react with the glass material. In addition, the core inserts also should have enough rigidity and excellent mechanical strength in order not to be scratched. Furthermore, the core inserts should be impact-resistant at high temperatures and under high pressures. Moreover, the core inserts should have excellent machinability in order that they may be machined precisely and easily to form the desired optical surfaces. Finally, the core inserts should have a long working lifetime so that the cost of manufacturing aspheric lenses is kept to a minimum. However, a typical contemporary core insert generally has a short working lifetime, which escalates the cost of producing aspheric lenses.
Plastic aspheric lenses are generally manufactured by way of injection molding. Though the cost of plastic aspheric lenses is relatively low, a plastic aspheric lens has a low image-forming quality compared to a glass aspheric lens. This difference in quality is due to the transparent quality of plastic being less than that of glass.
What is needed is an optical lens which has a lower cost and a better image-forming quality.